The present invention relates to laminated materials and the process for their production. The laminates have a layer of polyethylene bonded to a layer of an ultra-high molecular weight polyethylene high performance fiber. More particularly, the present invention relates to a method of producing a laminate by bonding a layer of a thermoplastic film such as polyethylene or ethylene vinyl acetate (EVA) to a layer of a strong, lightweight fabric constructed of a high performance fiber such as long chain expanded polyethylene fibers.
High performance fabrics have been used for a number of applications where tear-resistance, abrasion-resistance, cut- and stab-resistance, and chemical- and cold-resistance are important. As used herein, the term xe2x80x9chigh performancexe2x80x9d refers to fabrics constructed from a group of fibers used to make cut-resistant, and abrasion resistant articles such as gloves and aprons. The high strength-to-weight ratios of these fabrics can provide properties having significant improvements in the performance characteristics stated above at a fraction of the weight of other alternatives. It would be desirable to combine the advantages of high performance fabrics with film-laminated fabrics currently used for applications such as cargo container covers and side curtains for side-access trucks. These items typically are constructed from vinyl-coated nylon or similar materials which do not exhibit these high performance characteristics. The vinyl coating is provided for the purpose of creating an impervious barrier to air and fluid penetration. The disadvantages of currently available vinyl-coated nylon or polyester fabric materials is their relative lack of durability and relatively higher weight per unit area. Thus, it would be desirable to take advantage of the high strength and low weight characteristics of high performance fabrics for these applications. An successful lamination process for these fabrics would enhance their abrasion resistance. It is believed that no successful process has been developed for the economical lamination of high performance fabrics with a thermoplastic film such as polyethylene or EVA to create a more durable, waterproof, cut and wear resistant laminate.
The present invention relates to the heat lamination of a thermoplastic films to fabrics constructed of arrangements of fabrics constructed of high performance fibers such as high tenacity, high modulus, ultrahigh molecular weight polyethylene fibers. Various applications and potential applications of fabrics constructed of high strength polyethylene fibers require a flexible, light weight coating to prevent the penetration of the fabric by fluids, chemicals and particles. These applications require the high strength-to-weight of the high performance, polyethylene fiber fabrics and consequently require a coating that is equally lightweight. In addition the coating must stretch with the fabric and is required to be tough, abrasion resistant chemically resistant, well adhered and durable. Previously, high strength polyethylene fibers have not been coated or laminated with conventional coatings or films due to their extremely low functionality and highly crystalline structure. There are no bonding sites to chemically bond adhesives or coatings.
The method of the present invention includes making a cut and puncture resistant laminated fabric comprising laminating a layer of thermoplastic film to a layer of fabric comprised of a high performance yarn. The laminating step is conducted at a temperature between about 230xc2x0 F. and about 290xc2x0 F. with a contact time of between about 5 minutes and about 4 to 8 hours with the application of a laminating pressure of between about 50 psi and about 500 psi. The thermoplastic film may be comprised of a material selected from the group consisting of high density polyethylene, low density polyethylene and ethylene vinyl acetate. The high performance fiber is comprised of a material selected from the group consisting of extended chain polyethylene, ultra high molecular weight polyethylene, and aramid.
Thus one aspect of the present invention is to provide an economical method for lamninating a high performance fabric.
Another aspect of the present invention is to provide a method for making a lightweight sheet material having superior wear characteristics.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiments when considered in conjunction with the drawings.